Adapting to Climate Change: Assessing the World Bank Group ...

APPENDIX HADDITIONAL EVIDENCEkilometer of forest based on those areas that were protected, while ignoring the factthat the average benefit of avoided losses depends on the value of assets protected,which will not remain constant outside of the sample zone where mangroves wereplanted. Barbier (2007) uses an expected damage function approach that estimatesthe value of coastal protection benefits based on coastal disaster data and mangrovecoverage from Thailand, and find much lower values than are generated from areplacement cost approach. But weaknesses in the available data on disasterdamage, mangrove coverage, and other factors that drive disaster losses suggest thattheir point estimate (loss of one square kilometer of mangrove leads to an increase ofexpected storm damages of $585,000) should be interpreted with caution.Efforts to estimate the coastal protection benefits of mangroves are complicated by ahigh degree of spatial variation in impact, depending on topography, vegetationproperties, and the types of storms involved. For example, Kabir and others (2006)model the effect mangroves in reducing storm surge from a 1970 cyclone on HatiaIsland in Bangladesh. They find that while in some locations mangrove afforestationwith a width of 133-600 meters leads to reduction in storm surge height of 0.18-0.45meters, in other locations the protective benefits were negligible. Mazda and others(1997) study mangrove zone on the Tong King delta in Vietnam, and find nosignificant reduction in storm surge in areas with immature mangrove cover, butwave height reduction of 20 percent per 100 meters of mangrove in areas withsufficiently tall trees. Badola and Hussain (2005) measure economic losses in threevillages in Orissa hit by a 1999 cyclone, and find the greatest loss per household wassuffered in a village with an embankment but no mangroves ($153.74), followed by avillage with no embankment and no mangroves ($44.02) with the least damageoccurring in a village with mangroves ($33.31). The fact that a given storm has suchdrastically different effects on different villages (even those close to each other)makes it difficult to estimate the marginal value of mangrove cover because of theeconomic and geographic heterogeneity at the village level Das and Vincent(2009)evaluated the protective effect of mangroves for the same cyclone over a wider area,using geographical data on geophysical and socioeconomic factors. They found thatmangroves had a statistically significant protective effect and on average, for thisevent, one hectare of mangroves averted 0.0148 deaths.127